How does a ventouse vacuum extractor work?

This is a flattish or shallow cup-shaped apparatus, made of plastic or metal, that is connected to a vacuum tube. The vacuum cup is placed against the baby’s head (an episiotomy may not be required) and strong vacuum suction is applied. The doctor can then move the tubing handle to aid with rotating the head to help descend the baby. The ventouse can leave an obvious, swollen bruise on the baby’s head, called a chignon, which will fade in a few days (or hours).